A Simple Design and Simulation of Full Bridge LLC Resonant DC-DC Converter for PV Applications

 ABSTRACT:

This paper deals with the design and simulation of full bridge LLC resonant converter suitable for photovoltaic applications. LLC converter has several desired features such as high efficiency, low electromagnetic interference (EMI) and high power density. This paper provides a detailed practical design aspect of full bridge LLC resonant converter. The LLC converter is implemented with a full-bridge on the primary side and a fu l-bridge rectifier on the secondary side. It includes designing the transformer turns ratio and selecting the components such as resonant inductor, resonant capacitor and magnetizing inductor. Also performance parameters such as voltage gain and output voltage ripple are calculated. Simulation of LLC resonant converter is carried out using MATLAB / SIMULINK and the results are verified.

KEYWORDS:

1.      LLC resonant converter

2.       Output voltage ripple

3.      Voltage gain

SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:

Fig. 1: Simulink diagram of full bridge LLC resonant converter

EXPECTED SIMULATION RESULTS:

 Fig. 2: Driving pulse of MOSFET Q1&Q3, current and voltage waveforms

Fig. 3: Driving pulse of MOSFET Q2&Q4, current and voltage waveforms

 Fig. 4: Output voltage of inverter & current through resonant components

                                              

 Fig. 5: Transformer primary and secondary voltages

                             Fig. 6: Output current, output voltage and output power of LLC resonant converter

Fig. 7: Output ripple voltage waveform

CONCLUSION:

The design procedure of Full Bridge LLC Resonant Converter is presented for photovoltaic application. Theoretical values of resonant component values are calculated using the design equations. Simulation results are provided for LLC Resonant converter for an input voltage of 33V. The voltage gain and output voltage ripple of LLC resonant converter is calculated which shows that the ripple is less in the proposed converter.

REFERENCES:

1. Abramovitz, A. and S. Bronshtein, 2011. A design methodology ofresonant LLC DC-DC converter’ Power Electronics and Applications (EPE2011), Proceedings of the European Conference, pp: 1-10.

2. Bing Lu, Wenduo Liu, Yan Liang, F.C. Lee and J.D. Van Wyk, 2006.Optimal design methodology for LLC resonant converter’, Applied Power Electronics Conference and Exposition. Twenty-First Annual IEEE, 6: 19-23.

3. Choi, H.S., 2007. Design consideration of half bridge LLC resonant converter, Journal of Power Electronics, 7(1): 13-20.

4. Gopiyani, A. and V. Patel, 2011. A closed-loop control of high power LLC Resonant Converter for DC-DC applications, Nirma University International Conference, pp: 1-6.

5. Senthamil, L.S., P. Ponvasanth and V. Rajasekaran, 2012. Design and implementation of LLC resonant half bridge converter’ Advances in Engineering, Science and Management (ICAESM), International Conference, pp: 84-87.

Performance Improvement of Single-Phase Grid–Connected PWM Inverter Using PI with Hysteresis Current Controller

ABSTRACT:

Now a day’s distributed generation (DG) system uses current regulated PWM voltage-source inverters (VSI) for synchronizing the utility grid with DG source in order to meet the following objectives: 1) To ensure grid stability 2) active and reactive power control through voltage and frequency control 3) power quality improvement (i.e. harmonic elimination) etc. In this paper the comparative study between hysteresis and proportional integral (PI) with hysteresis current controller is presented for 1-Φ grid connected inverter system. The main advantage of hysteresis+PI current controller is low total harmonic distortion (THD) at the point of common coupling (PCC) at a higher band width of the hysteresis band. The studied system is modeled and simulated in the MATLAB Simulink environment.

KEYWORDS:

1.      Hysteresis current controller

2.       PI controller

3.       Point of common coupling (PCC)

4.       DG

5.       Utility grid

6.      THD

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig.1. Block diagram for hysteresis current control of single-phase grid connected VSI

EXPECTED SIMULATION RESULTS:

Fig.2. Simulation result of the hysteresis current controller for fixed band (a) grid voltage (Vg) and grid current (Io) (b) reference current, actual current and current error(c) switching frequency

Fig.3. Simulation result of the hysteresis+PI current controller for fixed band (a) grid voltage (Vg) and grid current (Io) (b) reference current, actual current and current error(c) switching frequency

Fig.4. Simulation result of hysteresis current controller for change in band (a) grid current (b) switching frequency(c) current error

Fig.5. Simulation result of hysteresis+PI current controller for change in band (a) grid current (b) switching frequency(c) current error

Fig.6. THD of grid current for hysteresis current controller (a) HB=1(b)HB=3(c)HB=5

Fig.7. THD of grid current for hysteresis+PI current controller (a) HB=1(b) HB=3(c) HB=5

CONCLUSION:

From the study we observed that, hysteresis+PI current controller can enable to reduce switching frequency even if the band width increased without any significant increase in the current error. Hence it provides considerably less THD at higher band width as compared to conventional hysteresis current controller.

REFERENCES:

[1] Blaabjerg, F.; Teodorescu, R.; Liserre, M.; Timbus, A.V., “Overview of Control and Grid Synchronization for Distributed Power Generation Systems” IEEE Transactions on Industrial Electronics,Vol.:53 , Issue:5, Page(s): 1398 – 1409, 2006

[2] F.Blaabjerg, Zhe Chen, and S.B. Kjaer. “Power Electronics as Efficient Interface in Dispersed Power Generation Systems”, IEEE Transactions on Power Electronics, 19(5):1184–1194, Sept. 2004.

[3] Ho, C.N.-M.,Cheung, V.S.P.,Chung, H.S.-H.” Constant-Frequency Hysteresis Current Control of Grid-Connected VSI without Bandwidth Control”,IEEE Trans. on Power Electronics, TPEL 2009,Volume: 24, no. 11 ,, Pp:2484 – 2495, 2009

[4] Rahman, M.A.; Radwan, T.S.; Osheiba, A.M.; Lashine, A.E.; “Analysis of Current Controllers for Voltage-Source Inverter” IEEE Trans. On Industrial Electronics, Volume: 44 , no. 4 , Pp. 477 – 485, ,1997

[5] Tekwani, P.N, Kanchan, R.S., Gopakumar, K.; “Current-error spacevector- based hysteresis PWM controller for three-level voltage source inverter fed drives” Proceedings of Electric Power Applications, IEE Volume: 152 , Issue: 5, Pp: 1283 – 1295,2005

Implementation of Hysteresis Current Control for Single-Phase Grid Connected Inverter

 ABSTRACT:

This paper describes a control method for single phase grid-connected inverter system for distributed generation application. Single-band Hysteresis Current Controller is applied as the control method. The control algorithm is implemented in Digital Signal Processor (DSP) TMS320F2812. The control method provides robust current regulation and achieve unity power factor. Simulation and experimental results are provided to demonstrate the effectiveness of the design.

KEYWORDS:

1.      Single-Phase Grid Connected Inverter

2.       Hysteresis Current Control and TMS320F2812

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig.1 Proposed hystresis current control for single-phase grid connected inverter

EXPECTED SIMULATION RESULTS:

Fig. 2 Error signal and hysteresis band

Fig.3. Switching pattern of hysteresis current control

Fig.4 Inverter output voltage before inductor

Fig. 5 Simulation result Grid voltage and Grid current

Fig. 6 Simulation result Grid voltage and Grid current at unity power factor

 CONCLUSION:

This paper presents a single-band hysteresis current control for single-phase grid connected inverter. The effectiveness of the control scheme has been verified both by simulation and experimentally. The current produced by this inverter is in phase with grid voltage and also achieve unity power factor. This method is robust and effective than conventional reference signal generation by the controller and matching it with the grid voltage at later stage. This method also reduces the number of components such as Phase Lock Loop (PLL) circuits and cost significantly.

REFERENCES:

[1] http://en.wikipedia.org/wiki/Distributed _ generation

[2] Kojabadi, et. al, "A Novel DSP-Based Current-Controlled PWM Strategy for Single Phase Grid Connected Inverters", IEEE Trans. on Power Electronics, Vol. 21,No.4, July 2000, pp. 985-993

[3] Bor-Jehng Kang and Chang-Ming Liaw, "A Robust Hysteresis Current-Controlled PWM Inverter for Linear PMSM Driven Magnetic Suspended Positioning System". IEEE Trans. on Ind. Electronics, Vol. 48, No. 5, October 2001, pp 956-967

[4] S. Buso, S. Fasolo, L. Malesani, and P. Mattavelli, "A Dead-Beat Adaptive Hysteresis Current Control" IEEE Trans. on Ind. Applications, Vol. 36, No.4 July/August. 2000, pp 1174-1180

[5] P.A. Dahono and I. Krisbiantoro, "A Hystersis Current Controller for Single-Phase Full-bridge Inverter". Int. Conf. on Power Electronics and Electric Drives 2001, Indonesia, pp 415-419

Model Predictive Control of PV Sources in A Smart DC Distribution System Maximum Power Point Tracking and Droop Control

ABSTRACT:

In a dc distribution system, where multiple power sources supply a common bus, current sharing is an important issue. When renewable energy resources are considered, such as photovoltaic (PV), dc/dc converters are needed to decouple the source voltage, which can vary due to operating conditions and maximum power point tracking (MPPT), from the dc bus voltage. Since different sources may have different power delivery capacities that may vary with time, coordination of the interface to the bus is of paramount importance to ensure reliable system operation. Further, since these sources are most likely distributed throughout\ the system, distributed controls are needed to ensure a robust and fault tolerant control system. This paper presents a model predictive control-based MPPT and model predictive control-based droop current regulator to interface PV in smart dc distribution systems. Back-to-back dc/dc converters control both the input current from the PV module and the droop characteristic of the output current injected into the distribution bus. The predictive controller speeds up both of the control loops, since it predicts and corrects error before the switching signal is applied to the respective converter.

KEYWORDS:

1.      DC microgrid

2.      Droop control

3.      Maximum power point tracking (MPPT)

4.      Model predictive control (MPC)

5.      Photovoltaic (PV)

6.      Photovoltaic systems

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. Multiple-sourced dc distribution system with central storage.

EXPECTED SIMULATION RESULTS:

                                   

Fig. 2. Ideal bus voltage and load power as system impedance increases and loads are interrupted to prevent voltage collapse. (a) Bus voltage decreases in response to increased system impedance at t₁ to reach the operating point on the new P–V curve at t₂ . The new bus voltage is below the UVP limit, so control action cause load to be shed, moving to a new operating point on the same P–V curve at t₃ with a higher bus voltage. (b) Load power in the system changes as point-of-load converters are turned OFF to reduce total system load when the bus voltage drops below the UVP.

Fig. 3. Response of dc bus voltage to step changes in the power drained by

load.

Fig. 4. Response of dc bus voltage and output power to imbalanced input

PV sources

                                       

. Fig. 5. Response validation of dc bus voltage to step changes in the power

drained by load.

 

Fig. 6. Response validation of dc bus voltage and output power to imbalanced

input PV sources.

 

Fig. 7. Response of dc bus voltage and output power to the input PV sources

of Fig. 7.

CONCLUSION:

High efficiency and easy interconnection of renewable energy sources increase interests in dc distribution systems. This paper examined autonomous local controllers in a single-bus dc microgrid system for MPP tracked PV sources. An improved MPPT technique for dc distribution system is introduced by predicting the error at next sampling time using MPC. The proposed predictive MPPT technique is compared to commonly used P&O method to show the benefits and improvements in the speed and efficiency of the MPPT. The results show that the MPP is tracked much faster by using the MPC technique than P&O method.

In a smart dc distribution system for microgrid community, parallel dc/dc converters are used to interconnect the sources, load, and storage systems. Equal current sharing between the parallel dc/dc converters and low voltage regulation is required. The proposed droop MPC can achieve these two objectives. The proposed droop control improved the efficiency of the dc distribution system because of the nature of MPC, which predicts the error one step in horizon before applying the switching signal. The effectiveness of the proposed MPPT-MPC and droop MPC is verified through detailed simulation of case studies. Implementation of the MPPT-MPC and droop MPC using dSPACE DS1103 validates the simulation results.

REFERENCES:

[1] Z. Peng, W. Yang, X. Weidong, and L. Wenyuan, “Reliability evaluation of grid-connected photovoltaic power systems,” IEEE Trans. Sustain. Energy, vol. 3, no. 3, pp. 379–389, Jun. 2012.

[2] W. Baochao, M. Sechilariu, and F. Locment, “Intelligent DC microgrid with smart grid communications: Control strategy consideration and design,” IEEE Trans. Smart Grid, vol. 3, no. 4, pp. 2148–2156, Dec. 2012.

[3] R. Majumder, “A hybrid microgrid with DC connection at back to back converters,” IEEE Trans. Smart Grid, vol. 5, no. 1, pp. 251–259, Jun. 2013.

[4] R. Lasseter, A. Akhil, C. Marnay, J. Stephens, J. Dagle, R. Guttromson, A. S. Meliopoulous , R. Yinger, and J. Eto, “Integration of distributed energy resources. The CERTS microgrid concept,” U.S. Dept. Energy, Tech. Rep. LBNL-50829, 2002.

[5] T. Esram and P. L.Chapman, “Comparison of photovoltaic array maximum power point tracking techniques,” IEEE Trans. Energy Convers., vol. 22, no. 2, pp. 439–449, Jun. 2007.